1. Field of the Invention
The present invention relates to an exposure apparatus and an exposure method for fabricating semiconductor devices or liquid crystal display boards, and more particularly to those with a plurality of illumination optical systems.
2. Related Background Art
The liquid crystal display boards have frequently been used as a display device for personal computers, televisions, etc. these days. The liquid crystal display boards are produced by patterning a transparent thin-film electrode in a desired pattern on a glass substrate by the technique of photolithography. Used as apparatus for the photolithography are projection exposure apparatus for performing exposure of a photomask pattern formed on a mask, on a photoresist layer on the glass substrate through a projection optical system.
There is a recent demand to increase the area of liquid crystal display board, with which the projection exposure apparatus are also demanded to have an enlarged exposure area. A scanning exposure apparatus provided with a plurality of projection optical systems is a conceivable means for expanding the exposure area. Namely, a light beam emitted from a light source is guided through an optical system including a fly's eye lens etc. to average quantities of light and thereafter the light beam is shaped in a desired cross section by a field stop to illuminate an area on a pattern surface of mask. A plurality of optical systems (illumination optical systems) of such structure are arranged to illuminate different small regions (illumination areas) on the mask with light beams emitted from the respective illumination optical systems. Light beams passing through the mask travel through respective, different projection optical systems to form pattern images of mask in different projection areas on the glass substrate. Then the mask and glass substrate are synchronously moved relative to the projection optical systems, whereby the entire surface of pattern area on the mask is transcribed onto the glass substrate.